An operating control system for a combustion furnace is provided with a monitoring module for monitoring interlocks pertaining to safety operations of the combustion furnace, and a combustion control module for controlling the operation of the burner in the combustion furnace. Furthermore, in the monitoring module, interlocks pertaining to safety operations of the combustion furnace are monitored, where only when the interlocks are in the normal state is a “burner operation permitted” signal sent to the combustion control module from the monitoring module, and the operation and the control of the burner is activated thereby. In this case, if, in the monitoring module, the interlocks are not in the normal state, then it is important, conversely, that the “burner operation permitted” signal not be outputted. It is also important that, in the combustion control module, that the “burner operation permitted” signal be recognized reliably.
Note that signals pertaining to these types of safety operations must be transmitted reliably, and, for example, Japanese Unexamined Patent Application Publication 2001-133502 (“JP '502”) discloses a technology for detecting a failure in a harness (an open line, a ground fault, or the like) through the provision of a voltage divider circuit at both ends of the harness, when transmitting two types of signals, “H” and “L”, through a harness. However, the technique disclosed in this JP '502 does no more than enable the handling of failures in the harness.
However, in transmitting the aforementioned signals pertaining to safety operations between modules, it is important that the “burner operation permitted” signal be outputted (transmitted) only when the interlocks on the sending-side module (the monitoring module) are normal. Given this, one may consider increasing the reliability through providing, in parallel, a plurality of control devices that each output the “burner operation permitted” signal when the interlocks are normal, for example, and performing the transmission only when the control devices all output the “burner operation permitted” signal.
On the other hand, in the receiving-side module (the combustion control module), it is important to recognize accurately that the signal for which the transmission has been received is the “burner operation permitted” signal. In contrast, instead of having to the “burner operation permitted” signal be simply, for example, an “H” level or an “L” level signal (voltage), one may consider having the signal itself be a pulse signal of a specific period, and adding to the signal element whether or not there is a skip in the pulse signal, to thereby transmit the information reliably.
However, even when using the pulse signal described above, the reliable production of a pulse signal is not necessarily limited to only those times wherein the interlocks are normal. That is to say, one may also consider the case wherein the pulse generating circuit is malfunctioning. Given this, one may consider control that outputs the pulse signal using a relay, together with control for reducing the pulse signal depending on the interlocks. However, when a relay is used in parallel, there are the new problems of not being able to control the output of the pulse signal due to a failure of a relay (that is, when a relay contact point fuses).
The present invention is based on the perspective described above, and the object thereof is to provide a system for transmitting signals between modules that enables reliable transmission, between modules, of information pertaining to the actuation of safety mechanisms.